Re: What is the fastest point of sail for a windsurfer? Why?

First off, if you happen to need a physic teacher at the Maui Ocean Academy please let me know.

Wind-surfing seems to be a lot like sailing in terms of the forces that must be manipulated for propulsion and stability. I answered a question on the force diagram of sailing Re: How does a sail boat work, according to vectors and many more explanations on lift, drag, and other aerodynamic considerations are available for sports and flight MS_search.html using keywords like lift, aerodynamics, spin

A site that explains the basics of the principles or aerodynamics in a pretty straight forward manner is:

AerodynamicsJCM.html

An excellent site for the physics of sports is:

K8AIT Principles of Aeronautics - Instructor

In fact, Aerodynamics in Sports Equipment, Recreation and Machines - Sailing - Instructor has fairly good historical background and common sailing term explanation of sailing. The explanation triangular sails pulling the boat is very good, and is something that is not intuitive.

The following diagram will help you visualize the author's explanation of the wind flow around the sail. This is an approximation limited by my artist ability.

                                     * approximate direction of travel
                                  *
                              *
                          *
                      *
                  *            (normal flow)
----------------------------------- approximate boundary of wind
                            wind channel (faster)
leeward             $$$$$$$$$$$$$$$  profile of the sail ($) 
               $$$$$$       wind channel (slower)
           $$$$$
        $$$
     $$$$
   $$         windward
 $$
$

The difference in flow creates a pressure difference (Bernoulli effect). 
With
lower pressure on the faster moving air side.

The literature on the physics/engineering of sailing is vast (show me the money). I recommend you start there. In science, understanding comes from intuition, and inituition comes from experience. Ironically, technical advances often come from trial and error or dumb luck. At least, until people start to understand the science behind the advances.

If you and your students can make the necessary leaps of intuition based on the differences between boats and surfboards and the effect of the ratio of rider weight to vessel weight, I think you could teach the rest of the world a few things.

Sincerely,

Tom "No Lift" Cull